1. Field of the Invention
Embodiments of the present invention generally relate to a completion operation. More particularly, the present invention relates to a method and an apparatus for transporting a tool into a tubular and performing an operation.
2. Description of the Related Art
The safe and continuous operation of hydrocarbon wellbores and pipeline networks is essential to the operators and users of such networks. Accordingly, such pipeline and wellbores are cleaned and inspected at regular intervals to ensure their operational integrity.
The conventional approach to inspection of operating pipelines is for the tubular string to be precleaned several times using a “dumb” pig. The dumb pig, without any on-board intelligence, typically operates to scrape and remove debris such as wax, scale, sand, and other foreign matter from the tubular. In a newly formed pipeline with a new tubular string, the step of precleaning may not be required. In either case, a detailed inspection is subsequently performed by a “smart” pig, which makes detailed measurements of the tubular string to determine the internal condition of the tubular. The smart pig may also be employed to transport a tool to a predetermined location in the tubular string to perform various operations therein. The smart pig is typically equipped with technologies of varying sophistication. For example, the smart pig may include a mechanism for measuring an interior surface of the tubular string. In another example, the smart pig may include techniques such as magnetic flux leakage (MFL) or ultrasonic scanning (at various positions along the tubular string) to detect flaws or defects, which might prejudice the tubular's integrity. In other examples, the smart pig may include complex tools generally comprising arrays of probes and sensors for placement of on-line monitoring equipment for later collection or for precise placement of isolation components and radioactive devices.
One shortcoming of conventional pigging inspection operations is that a complicated technique is typically required to position the smart pig at a predetermined location in the tubular string prior to the inspection of the tubular string. For example, one technique requires reversing the flow of fluid in the tubular string to direct the smart pig in the desired direction. This manipulation of the fluid flow may cause numerous problems such as storage problems and production problems. Another technique requires additional components to be constructed adjacent to the tubular string such as a sub-sea pig facility or a second line. These components are used to introduce the smart pig to the predetermined location in the tubular string so that the smart pig can conduct an inspection of the tubular string as it returns to the platform with the flow of fluid in the tubular string. For instance, the second line is constructed adjacent to the tubular string to provide a fluid pathway to pump the smart pig from the platform to the predetermined point in the tubular string. However, these additional components increase the cost of the conventional pigging inspection operation and add undesirable complexity the completion operation.
In a similar manner, a cleaning apparatus or an inspection apparatus may be employed in a wellbore by urging the cleaning apparatus or the inspection apparatus through the wellbore on a string member. However, this technique increases the cost of the wellbore operation.
More recently, an apparatus commonly known as a tractor has been developed that is capable of entering a tubular string at a predetermined point of the tubular string and traveling through the tubular string. The tractor subsequently returns through the same tubular string back to the predetermined point. However, the tractor has not been effectively utilized in conjunction with a pig or other inspection or cleaning tools requiring transportation through a tubular string.
A need therefore exists for a method and apparatus of using a tractor in conjunction with other tools to transport and/or place tools in a pipeline or a wellbore.